Kilogram-Scale Fabrication of a Robust Olefin-Linked Covalent Organic Framework for Separating Ethylene from a Ternary C₂ Hydrocarbon Mixture

Abstract

One-step adsorptive purification of ethylene (C₂H₄) from a ternary mixture of acetylene (C₂H₂), C₂H₄, and ethane (C₂H₆) by a single material is of great importance but challenging in the petrochemical industry. Herein, a chemically robust olefin-linked covalent organic framework (COF), NKCOF-62, is designed and synthesized by a melt polymerization method employing tetramethylpyrazine and terephthalaldehyde as cheap monomers. This method avoids most of the disadvantages of classical solvothermal methods, which enable the cost-effective kilogram fabrication of olefin-linked COFs in one pot. Furthermore, NKCOF-62 shows remarkably selective adsorption of C₂H₂ and C₂H₆ over C₂H₄ thanks to its unique pore environments and suitable pore size. Breakthrough experiments demonstrate that polymer-grade C₂H₄ can be directly obtained from C₂H₂/C₂H₆/C₂H₄ (1/1/1) ternary mixtures through a single separation process. Notably, NKCOF-62 is the first demonstration of the potential to use COFs for C₂H₂/C₂H₆/C₂H₄ separation, which provides a blueprint for the design and construction of robust COFs for industrial gas separations.